1. Field of the Invention
The present invention relates to an X-ray diagnostic apparatus having a floor type C-arm.
2. Description of the Related Art
Medical image diagnostic techniques using X-ray diagnostic apparatuses, MRI apparatuses, and X-ray CT apparatuses have rapidly advanced with improvements in computer technology, and have become indispensable to current medical practice.
Recently, X-ray diagnosis has advanced mainly in the field of circulatory organs with improvements in catheter techniques. An X-ray diagnostic apparatus for the diagnosis of circulatory organs generally comprises an X-ray generating unit, an X-ray detecting unit, a holding apparatus which holds the X-ray generating unit and the X-ray detecting unit, a bed (top), a signal processing unit, a display unit, and the like. The holding apparatus allows X-ray imaging at an optimal position or in an optimal direction by pivoting, rotating, or moving a C-arm or Ω arm around a patient (to be referred to as a subject hereinafter).
As a detector used for the X-ray detecting unit of an X-ray diagnostic apparatus, an X-ray film or an I.I (Image Intensifier) has been used. In an X-ray imaging method using this I.I, X-ray projection data (to be referred to as projection data hereinafter) obtained when X-rays generated by the X-ray generating unit are transmitted through a subject is converted into an optical image by the I.I, and this optical image is displayed on a monitor after being converted into an electrical signal by an X-ray TV camera and A/D-converted. Therefore, the X-ray imaging method using the I.I allows real-time imaging which is impossible in the film system, and can acquire projection data in the form of digital signals. This makes it possible to perform various kinds of image processing. As a substitute to the above I.I, a flat panel detector comprising a two-dimensional array of detection elements has recently attracted attention. The replacement of such detectors is rapidly advanced.
FIG. 9 shows a C-arm holding apparatus used for a conventional circulatory organ X-ray diagnostic apparatus. An X-ray generating unit 1101 is mounted on one end (lower end) of a C-arm 1103 of a C-arm holding apparatus 1110, and an X-ray detecting unit 1102 comprising, for example, a flat panel detector is mounted on the other end (upper end) of the C-arm 1103 so as to face the X-ray generating unit 1101. A one-dot dashed line 1108 in FIG. 9 represents an imaging axis which connects the focal point of an X-ray tube in the X-ray generating unit 1101 to the center of the flat panel detector of the X-ray detecting unit 1102. The dot dashed line indicates a central line when a table top 1107 is at a lateral reference position, and a base line BL as a reference for an image posture which almost coincides with the body axis of the subject at the time of imaging operation.
The C-arm 1103 is held on a stand 1105, fixed on a floor surface 1106, through an arm holder 1104. The C-arm 1103 is mounted on an end portion of the arm holder 1104 so as to be slidable in the direction indicated by an arrow a. The arm holder 1104 is mounted on the upper portion of the stand 1105 so as to be pivotal or rotatable in the direction indicated by an arrow b. The stand 1105 comprises a stand fixed portion 1105a fixed on the floor surface 1106 and a stand movable portion 1105b which can pivot about the column axis in the direction indicated by an arrow c.
The X-ray generating unit 1101 and X-ray detecting unit 1102 (to be collectively referred to as an imaging system hereinafter) are set at an optimal position in an optimal direction with respect to a subject (not shown) placed on the table top 1107 by sliding the C-arm 1103 in the direction a and pivoting the arm holder 1104 in the direction b. In addition, the imaging system and the C-arm 1103 can be retracted from the subject by pivoting the stand movable portion 1105b in the direction c. Retracting the imaging system and the C-arm 1103 makes it possible to ensure a working space around the jugular of the subject for a doctor or an examiner (to be referred to as an operator hereinafter) and facilitate replacement or repositioning of the subject on the table top 1107 before or after the examination, placement of anesthesia equipment, and the like.
Note that as the arm holder 1104 described above, an L-shaped offset arm is generally used as shown in FIG. 9. Making the arm holder 104 L-shaped allows the C-arm 1103 to be placed on a side of the table top 1107. This makes it possible to move an end portion of the table top 1107 in the longitudinal direction to near the stand 1105 in the direction indicated by an arrow d. That is, using the L-shaped arm holder 1104 makes it possible to widen the moving range of the table top 1107 and hence the imaging range with respect to the subject. In addition, the L shape of the arm holder 1104 has an advantage of being able to ensure a working space around the jugular of a subject for an operator.
However, the ensurance of a working space or the widening of the imaging range by pivoting the stand movable portion 1105b or using the L-shaped arm holder 1104 has its own limit because the stand 1105 is fixed on the floor surface 1106, and hence is not necessarily sufficient for the operator.
In order to solve such problems, a method has been proposed in which a ceiling-mounted C-arm holding apparatus having an arm whose one end is pivotally mounted on the ceiling and an arm holder mounted on the other end of the arm is used, and an imaging region of a subject can be arbitrarily set by aligning the position of the pivot axis of the arm with the central line of a table top in the longitudinal direction (see Jpn. Pat. Appln. KOKAI Publication No. 2000-70248).